1. Field of the Invention
The present invention is directed to assisting in lubricating the joints of mammals and methods of treating osteoarthritis and joint-related pain and ailments.
2. Description of Related Art
Synovial joints such as hip, knee, shoulder and ankle joints are surrounded by an envelope or synovial capsule. The inner layer of the synovial capsule is called a synovial membrane which produces synovial fluid. The fluid is partially stored within the joint cartilage and the remaining fluid circulates freely within the synovial capsule. The capsule maintains the fluid within the joint. In a hip joint, a ring of soft tissue called the acetabular labrum aids in maintaining the fluid in the femoral-acetabular interface. The fluid lubricates and thus reduces friction inside of the joint. In ball and socket synovial joints, the fluid lubricates the ball and socket interface, particularly during movement. For example, the wringing action of the synovial capsule in a hip joint, particularly during flexion and extension movement of the joint, and the paddling action of the femoral neck combine to pump synovial fluid into and across the femoral-acetabular interface thus lubricating the joint. The synovial fluid also cushions the joints during movement, provides oxygen and nutrients to the joint cartilage and removes carbon dioxide and metabolic waste.
Synovial fluid is generally composed of hyaluronic acid, lubricin, proteinases, and collagenases. The hyaluronic acid imparts anti-inflammatory and pain-reducing properties to the normal synovial fluid and contributes to joint lubrication and cushioning during movement. Synovial fluid also exhibits non-Newtonian flow characteristics and thixotropy where the fluid viscosity decreases over time under stress due to movement.
A lack of synovial fluid within the joint, particularly within the ball and socket interface, can aggravate arthritic conditions. Osteoarthritis, the wear and tear of aging, and other injuries or ailments can cause irregularity of the joint surface. In a hip joint, osteoarthritis can also cause fraying of the acetabular labrum resulting in the loss of its gasket-like sealing property. The fraying of the labrum allows migration of the synovial fluid away from the femoral-acetabular interface. Gravity also acts on vertical synovial joints such as hip joints by drawing the synovial fluid downward and away from the femoral-acetabular interface. Moreover, the stress and/or inflammation in synovial joints over time reduce the viscosity of the fluid making it a less effective lubricant and more difficult for the fluid to effectively coat the joint interface. This reduction in synovial fluid flow in the joint interface often results in further reduction in the sealing capacity of the labrum and roughening or incongruity of the joint interface causing increased pain and stiffness in the joint. The pain and stiffness causes a decrease in the motion of the joint resulting in a loss of the pumping action and decrease in the flow of the synovial fluid in the joint interface. This can eventually lead to joint replacement surgery.
To address this problem, artificial lubricants have been developed to replace and/or supplement the lubricating and cushioning action of the synovial fluid in the joint. These lubricants are generally referred to as viscosupplements and generally include hyaluronic acid. However, the degradation of the acetabular labrum associated with osteoarthritis can result in leakage and decreased flow of the viscosupplements. Thus, multiple viscosupplement treatments can be required.
Others have proposed the injection of biodegradable microparticles containing therapeutic agents into the arthritic joints. U.S. Patent Application Publication Nos. 2007/0141160 and 2010/0016257 to Brown, et al. disclose a method of treatment that includes intra-articular injection of biodegradable, polymer microparticles in a carrier vehicle. The microparticles are 5 to 150 microns and may be introduced with a carrier vehicle such as one including a therapeutic agent, for example, hyaluronic acid. The composition is injected into the intra-articular space of a joint to treat joint pain associated with osteoarthritis.
Other treatments to address this issue include joint replacement surgery, arthroscopic surgery, medication and physical therapy. Joint replacement surgery includes replacement of the joint with a prosthetic implant. The prosthetic implant may be constructed of various materials including metal and polymer materials. In addition the typical health risks associated with major joint surgery in older patients, risks and complications of the procedure include infection, dislocation, loosening, or impingement of the implant. In hip replacement surgery, the risks also include fractures of the femur. Moreover, the implant may wear over time causing dissemination of metal and polymer debris within the joint and body, in general.
There exists a need in the art for other innovative methods to improve joint lubrication and thus address the degradation and reduction in the circulation of synovial fluid associated with aging, osteoarthritis, injuries and other ailments. The method will preferably relieve pain and extend joint life to avoid the drawbacks associated with joint replacement surgery and to improve on existing treatments.